2013/01/22

Hi a quick note, if you are using Windows 8 and Team Foundation Service and you get to the point where you do not get a login prompt and just keep getting an Unauthorised access message. (I.e. you use a different live ID for TFS than you use for Windows 8) The trick to getting it working is to delete browsing history and cookies in IE/Internet options.

2013/01/07

The WordPress.com stats helper monkeys prepared a 2012 annual report for this blog.

Here’s an excerpt:

600 people reached the top of Mt. Everest in 2012. This blog got about 5,900 views in 2012. If every person who reached the top of Mt. Everest viewed this blog, it would have taken 10 years to get that many views.

2012/12/19

Spent last weekend and some of the start of my Xmas holiday trying to finalise the plumbing between my three tiers.

There are now two types of services in the middle tier.

OData read-only service. This is where things like the web client can get access to the game entities that get generated and allow for the game codex to be built. These will remain open and available to anyone that wants to view them.

Updates and membership information. This will be a WCF based service mainly due to requiring the “Updates” to be sent over the service bus to the back end part of the system. And this is what will end up being secured at a later date when I’ve managed to research it more.

The only part of the feed currently available is the Latest News feed which is shown on the front page of the client web site currently.

There is also a hidden part of the client website which handles adding new news articles.

This is basically how adding a new news article works…

Client Website sends a news article to the middle tier WCF Service AddNewsArticle

The middle tier web service generates a GUID (Checking job result list in the DB to make sure it doesn’t already exists) and then creates a Service Bus “Job” which contains the GUID and passes GUID back to client.

The back end tier receives the news article job and then adds the article to the database and writes an entry in the job result list saying that it successfully created or it failed to create the news article using the GUID as a key.

While the back end is processing this job the web client has requested the job result from the middle service tier using the GUID key it recieved earlier. This service will wait up to thirty seconds for the job result to be generated (Checking every second) and then return the result back to the web client. It will also send a job to the back end to delete the job result.

The web client will either go back to the front page and the news article will then be displayed, or if there was an error, it will display the error on the add news article page so the user can decided what to do (I.e. me try to fix it 😉 )

The upshot all this recent work on the plumbing side of things means that I can now proceed and create the more interesting bits of the game and hopefully make very few changes to the way the plumbing works.

The heart of this system is the Job that passes from the Service Tier to the Back end Tier. All the code required to do a “Job of work” is held in these jobs. All the service tier has to do is create a job of a specific type and populate the required information, then send this job over the service bus to the back end. All the back end has to the is “Process” the job which makes the back end very small and simple in the way of code. All the work is done in the Job Process function. Hence most of the future development will be in these jobs and the client.

2012/12/12

The OData feed now has it’s first collection. As an initial test I created a news feed to keep the website updated on progress. I’ve not done the code to update the news feed just yet as I’m investigating securing WCF Rest services with the Azure ACS (Planning to go through the Windows Identity Foundation Patterns: On-Premise and Cloud Pluralsight course to help with this)

But the website now consumes this feed by displaying the last 5 news articles on the front page:

Another weekend on hacking code to get the Tyrannt project off the ground. Again I am concentrating on the middle OData web service tier. One of the rules I set myself was to not allow this tier to update the database. These update requests are only meant to be done on the back end tier via messages passed along the Azure Service Bus (ASB).

After an initial hiccup which resulted in my WCF service request falling over with “Not enough memory” (These are hosted in Azure extra small compute instances). I managed to get a working service in the cloud that exposed all my current tables.

Next I wanted to split the tables over multiple data services. I initially achieved this by creating multiple database contexts. This also allowed me to intercept the SaveChanges call in the database context when someone did a Post or Put (Below is my current thinking of how to do this, although this may change when I find it doesn’t work 😉 )

But when it came to trying to actually run this, I kept getting an error saying:

The model backing the 'TyranntSubsetContext' context has changed since the database was created.

After a lot of searching it seemed like some people said this was possible and other said it was not. I decided to change tack and use a single database context that had all my tables in it, but make a duplicate one in my service project which I can use to intercept the saves. (The Back end tier will need normal database access as this will be doing the writes)

Anyway I still needed to expose different tables in different services. And as a nice surprise this time, it was very easy to do.

After doing a lot of searching around on the web. I could not find any solution to this, so I started to go through removing references. (Thinking that something I added with Nuget is causing the conflict)

I removed the System.Data.Services.Client reference and Everything started working again.

I then used the Object Explorer which showed that DataServiceProtocolVersion now resided in the:

Microsoft.Data.Services.Client

Assembly.

Just posting this in case I can help save some time for anyone else who is suffering from this issue.

I spent most of this weekend, researching different ways to achieve my project. There are certain things that I know I want to do:

Adopt a Three Tier Approach.

Multiple Clients (Including a Website)

A middle service layer that all the clients talk to which can read from the database but not update.

A back end which is the only part of the solution allowed to update the database

The communication between the middle tier and the back end tier will be via the Azure Service bus.

I want the user of the application to be able to log in to the various client using their Windows Account/Google/Facebook ID’s.

With this in mind I was looking into ways to achieve these goals. I was mainly concentrating on what the middle service tier should be.

I wanted something that will make it easy to implement clients on non Microsoft platforms which drew me towards using the new ASP.Net MVC Web API. The downside of this is there is no metadata to describe the service which makes the client much harder to write. After a few discussions with a colleague, they suggested using WCF OData service which should allow making clients easy on the windows side. (Automatic generation of model classes when adding a service reference)

But I’m still open to suggestions from anyone reading this if they think there may be a better way.

The solution structure for the project as it stands now will be:

Tyrannt.Model (Holds the Code First EF Classes)

Tyrannt.Backoffice (Windows Azure Worker Role – The back end tier)

Tyrannt.OData (Web Role – the Middle WCF OData tier)

Tyrannt.Website (First client – will consume the OData service)

I would also like to make use of database migrations that are in Entity Framework 5. Which also brings up another question which it’s been hard to answer. Where is the best place to put the Database context. An easy solution would be to put one in both the Backoffice and OData projects but that means maintaining two separate classes that basically do the same job)

I’ve seen some posts about not having the database context in the same project as the Model classes. I’m trying to work out the best way to do this and still allow database migrations.

Feel free to comment this posts with suggestions ideas or even telling me that I’ve got it all wrong ;-).